1. Field of the Invention
The present invention is in the field of key cutting devices, and more particularly in the field of cutting devices of the type wherein a pattern key to be duplicated serves as a guide for a stylus assembly which controls the relative movement of a key blank to be cut and a cutting or milling wheel in such manner that the desired pattern is cut in the blank.
2. The Prior Art
As is well known, a conventional means of forming a replacement key involves clamping an existing key and a key blank on a carriage in a predetermined spaced relationship. A rotary cutter and stylus are mounted on a frame, the spacing between the cutter and stylus corresponding to the spacing between the cut key and the key blank. By manually or automatically scanning the bitted surface of the cut key across the stylus (either by holding the stylus and cutter in fixed position and moving the carriage or vice versa), the key blank is caused to move through a similar pattern relative to the periphery of the rotary cutter, whereby a pattern corresponding to the pattern of the original key is formed on the surface of the blank.
It will be readily recognized that since the bitted portion of the cut key is used to lift the disks or tumblers of a lock, the newly cut key must conform with great accuracy to the dimensions of the pattern or original key. Differences in cut depth measuring in the thousandths of an inch may be sufficient to render the duplicate key inoperative.
It is of course desirable that duplicate keys be made as rapidly as possible since in locksmithing establishments the customer must often wait while the cutting is being effected. As a means for expediting the cutting, especially where multiple duplicate keys having the same bitted pattern are desired, certain key cutting machines have been developed which are capable of simultaneously cutting two blanks. Such devices have heretofore comprised a vise assembly having a first clamp for the pattern key and having a longitudinally spaced pair of clamps to support the key blanks. The motor shaft or a shaft driven thereby is typically provided with a pair of milling wheels displaced axially along the shaft at spaced positions corresponding to the spacing of the clamps supporting the key blanks. The blanks are cut to the pattern of the original key which, as hereinabove noted, is scanned across the surface of a stylus and carries with it the key blanks which are concomitantly moved across the spaced cutters.
Although devices of the type described have been successfully utilized to expedite the production of cut keys by enabling two such keys to be formed in the course of a single tracing operation, certain drawbacks inhere in multi-blank cutters heretofore known which have greatly impeded their widespread and successful use. Specifically, it is not uncommon for the blanks which are simultaneously processed to be cut to differing depths, whereby one or both of the keys may prove inoperative.
I have determined that a principal cause of such inaccuracy in machines of the type described resides in the fact that such machines are often employed to cut only one blank. As a result, over a period of time a condition may develop wherein one of the two cutting wheels will have received substantially greater use than the other, with the result that the overall diameter of the more frequently used wheel will be less than that of the less frequently used wheel. When such condition exists, the blank cut by the less used milling wheel will be cut to a greater depth than the other blank.
While it is feasible to compensate for wear, readjustment of the alignment of the stylus and cutters is a time consuming task and the normal tendency in locksmithing establishment is to put off the alignment operation. Often it is not until customers have complained of improperly cut keys that the inaccuracy is noticed and readjustment effected.